Just TheFishGuy's 2 cents............I would probably just go with a canister filter for a 55.
To move that amount of water, a canister would be your best bet.
The overflow box is going to take up a bunch of room in a 12 inch wide tank, and the 55 is also rather shallow for the overflow box.
Ned's has a large selection of canister filters in stock.
The new Eheim filters work GREAT!!!
They get TheFishGuy's 2 thumbs up.